1. Field of the Invention
The field of this invention relates to flashlights and other portable lighting devices, which are used in the home (inside and outside), in automobiles, for personal safety and emergency uses, for camping and recreation, for construction, for law enforcement uses, etc. More specifically, this invention relates to flashlights and other portable lights that have the charging and power storing mechanisms contained within them, wherein there is no need for batteries or an external electrical power source to charge the portable light. This invention also relates to portable lights that can be charged in a variety of ways from external electrical sources.
2. Discussion of Related Art
Ordinary flashlights and portable lights have been in use for many years throughout the world. The most popular kinds of flashlights and portable lights use disposable batteries and replaceable light bulbs. There are also a number of portable lights available today that contain rechargeable batteries, typically used in connection with home recharging units in which plugging the light into an ordinary home electrical outlet will charge the batteries. However, eventually these kinds of portable lights need new batteries, as the rechargeable batteries become depleted and incapable of holding a charge after extensive use.
There would be many advantages in having a portable light that never needs a change of batteries, never needs a bulb replacement, and never needs to be charged from an electrical power source. The applications for such a light include inside and outside home use, automobiles emergency use, camping, bicycling, general emergency use, construction and law enforcement uses, and numerous uses in underdeveloped countries. Such a light would also represent an economic and ecological advantage in reversing the environmental impact of discarded batteries, such as nickel-cadmium batteries; the most commonly used, highly toxic, rechargeable battery. Such a light also represents a very important advantage in situations or countries where no batteries, no bulbs and no electrical power sources are available, or where batteries are expensive or of poor quality.
The most popular flashlights and portable lights used in the world today are described in U.S. Pat. No. 4,032,773, U.S. Pat. No. 4,041,304, U.S. Pat. No. 4,151,583 and closely related prior art. These flashlights have one or more disposable batteries, a single on/off switch, and a light bulb backed by a reflective cone and covered with a glass or plastic lens. The major problem with these types of flashlights are that the battery charge decays with use and the batteries must be replaced regularly. This is costly, inconvenient, and has a negative environmental impact. In addition, the bulbs burn out and require replacement costs and wasted time in locating new bulbs.
Rechargeable flashlights and portable lights have been described in several United States patents, including: U.S. Pat. No. 3,787,678; U.S. Pat. No. 3,829,676; U.S. Pat. No. 4,045,663; U.S. Pat. No. 4,819,139; U.S. Pat. No. 4,794,315; U.S. Pat. No. 4,325,107; and U.S. Pat. No. 4,357,648. The portable lights disclosed in these patents have rechargeable batteries that last many times longer than the typical disposable batteries in typical flashlights. However, the principal problem with rechargeable battery flashlights is that the rechargeable batteries wear out and must be replaced, and these batteries, which are often nickel-cadmium batteries, pose dangerous problems to the environment if not disposed of properly. Another problem with this type of portable light is that recharging requires a connection to an external power source, usually a home outlet. This charging has the drawback of using some electricity at some cost, but more importantly it is inconvenient if one is away from home.
Other portable lights using solar cells for charging the batteries have been described in U.S. Pat. No. 5,621,303, and EP 5,3143,8A1. The devices disclosed therein use rechargeable batteries that wear out and require replacement.
A portable light with a hand-crank generator has been described in U.S. Pat. No. 4,360,860. This light also has the problem of the rechargeable battery needing replacement at some time.
U.S. Pat. No. 5,782,552 describes a light used for highway signaling purposes, which employs a solar panel for charging, a capacitor for electrical storage and a blinking LED for the signal light. This patent describes a specific circuit for charging the capacitor when light is available and automatically energizing the blinking LED when ambient light is below a pre-determined level, and a means to stop energizing the LED when the ambient light is above a pre-determined level. This art does not describe the use of a bright-white LED (non blinking), which is used in the present invention for the source of light. In addition, the ""552 patent makes no reference and provides no means of using the system for flashlights, portable lighting for home, recreation, automobile or emergency uses.
U.S. Pat. No. 5,975,714 describes a rechargeable flashlight using a capacitor for energy storage, an LED for light, and a linear motion generator to generate the power that is stored in the capacitor. This portable light has several problems. First, it uses a small Farad capacitor, (1 Farad), which holds enough power for only about 5 minutes of light. Secondly, this portable light provides no other means, other than the shaking, to charge the capacitor. One final problem with the ""714 is that the light intensity fades quickly; it starts out at full brightness, within one minute it is at half brightness, at 2 minutes it is at xc2xc brightness, and after 4 minutes it is about 8% of full brightness.
The flashlight and portable light of the present invention overcomes the battery replacement and disposal problems associated with known art by using a super capacitor for storage of electricity rather than any type of battery. As a result battery replacement is entirely obviated. The super capacitor used in this invention can be recharged and discharged over a million times without losing its ability to hold a full electrical charge. In addition, if disposal of a super capacitor is ever necessary, it poses no environmental hazard as it is made of environmentally friendly activated charcoal.
The present invention overcomes electrical charging problems associated with much of the prior art by using an exterior solar panel to charge the storage capacitor. When sufficient light is available, the solar panel generates electricity that is then stored by the capacitor. Three additional charging options are provided in the present invention, including a home charger unit, a car charger unit, and a crank-generator charger (internal or external). The home charger and the car charger can charge the capacitor in this invention fully in 30 seconds. Either one of these chargers can be plugged into the body of the present invention via a conventional charging receptacle or plug for charging, or the charging circuitry can be incorporated into the body of the portable light so that either an AC plug or a cigarette lighter plug can extend from the unit for connection to either outlet. In the portable light embodiment having a crank-generator charger, the rate at which the capacitor is charged varies according to how rapidly the crank is turned and how many revolutions are completed.
The present invention overcomes the bulb replacement problem by using a high brightness white LED (light emitting diode). The LED used in this invention is rated to last for up to 50,000 hours in continuous use. This means that the light source (in this instance the LED) would, for all practical purposes, never need replacement. The LED uses much less power than the typical incandescent bulbs used in most conventional flashlights because very little energy is lost in the form of heat (incandescent bulbs waste large amounts of power to heat); thus a super capacitor becomes feasible for energy storage because an LED requires much less power. By using a high brightness LED that provides continuous light, the present invention also overcomes the problem associated with the device disclosed in the ""552 patent that employs a colored and blinking LED.
By using an inverter circuit specifically developed for the present invention which produces constant current and voltage to the LED for a constant intensity of light during the cycle of power use from the super capacitor, the present invention solves the prior art problem of light brightness decay as voltage from the capacitor drops off. In addition, in an alternative embodiment, the present invention provides a means to increase or decrease brightness of the portable light by incorporating more than one LED. In this design, if one wants to conserve energy, one LED is turned on; if one wants more light, two or more LEDs can be turned on as needed. This feature allows the portable light of the present invention to provide light for a long period of time when using one LED as the light source, or to provide a much brighter light when it is needed, albeit for a shorter period of time. In addition, means are provided to lower the current to xc2xd or xc2xc to one LED to further conserve power if desired.
The present invention consists of a solar panel (comprising a plurality of electrically connected photovoltaic cells) that produces power to charge a high farad capacitor. A blocking diode is in line to prevent current leakage back to the solar panel when it is not charging. A voltage limiting circuit is in line with the solar panel, to limit the voltage going to the capacitor to prevent overcharging of the capacitor. In one configuration of this invention, when a switch is turned on, power stored in the capacitor travels to an inverter circuit which increases the voltage to the proper level for the LED, and at the same time, keeps the current steady at the maximum amount for the LED. This circuit keeps the voltage and current constant during the duration of power use from the super capacitor as the voltage varies from 2.6 volts DC to 0.9 volts DC. The LED is an integral part of this inverter circuit, and it also provides the light output.
The present invention uses two methods to produce the correct voltage and current from the capacitor to the LED. This is because the capacitors used in this invention are 2.5 volts DC and the high brightness LED requires 3.2-4.0 volts DC. The first method involves the inverter circuit mentioned in the above paragraph. This circuit operates to produce the correct voltage and current to the LED and to keep the voltage and current constant during the complete cycle of power use from the super capacitor. In this configuration, the light produced by the LED is constant for the whole duration of power use from the capacitor, which lasts for approximately 62 minutes when one 100 Farad super capacitor is used.
The second method involves a switching method in which two capacitors are charged in parallel at 2.5 volts via the solar panel, home/car chargers or crank-generator charger (the capacitors cannot be charged in series), then when the on/off switch is turned on to energize the LED, this switch switches the two capacitors from parallel to series, thereby bringing the voltage from 2.5 volts to 5 volts DC. A series resistor is used to bring the current to operating levels for the LED. In this configuration, the light from the LED starts at full brightness mid gradually fades as the voltage of the capacitors drops off. This configuration uses two 50 Farad super capacitors or two 100 F capacitors, and about 1xc2xd to 2 hours (or 3-4 hours if two 100 F capacitors are used) of light will be produced before the capacitors need recharging.
Means are provided in the present invention to charge this portable light with a portable charger plugged into a home outlet, and a portable charger plugged into a cigarette lighter in an automobile. With both of these chargers, the actual charging of the storage capacitor is very fast depending on the current output of the charger. Charging of a 100 Farad capacitor using a 10 Amp current at 2.5 V, DC (provided by a home charger or a car charger) will charge the capacitor in approximately 30 seconds. This fast charging represents a substantial advantage over conventional rechargeable flashlights, which typically take 3 hours or more to charge fully. A capacitor charges quickly because there is very little restriction in its ability to take on a charge.
The combination of a solar panel, optional home and car chargers (or a crank-generator) a 100 farad super capacitor for electricity storage, and a high brightness white LED for light produces a portable light that can hold enough electricity for one to two hours of light before needing to be recharged. Super capacitors of up to 100 farads are now available at economical costs for use in flashlights and other portable lights. Larger storage capacities are accomplished by adding additional capacitors (i.e. when two 100 F capacitors are used in a flashlight, light for up to 2-4 hours is produced, depending on the mechanism used to transfer power to the LED). The super capacitors of the present invention are small enough in size to be used in very portable lights (a typical 100 F at 2.5 Volts capacitor measures 3.5 cmxc3x975 cm.). Smaller, more portable and less expensive flashlights are included in the present invention using other size capacitors such as 20 F and 50 F in addition to 100 F capacitors, although all these sizes of capacitors were tested in the prototyping of this invention and the 50 F and 100 F capacitors performed the best in their ability to hold a charge. Therefore the 50 F and 100 F capacitors are the preferred storage capacitors used in this invention. Furthermore, the 100 F capacitors performed the best in holding a charge. Our testing showed that once a 100 F capacitor was charged fully, it would loose about 23% of its useable power (2.5 V to 0.9 V) after 6 weeks, and about only about 30% of its useable power after 3 months. This indicates that these super capacitors store power longer than typical nickel cadmium rechargeable batteries.
The preferred embodiment of this invention uses the previously described inverter circuit to increase voltage and keep current constant from the capacitor to the LED. Because this circuit is able to operate within a voltage input range of 0.9 V to 1.7 V, DC, a single dry cell 1.5 V battery can also be used to drive this circuit. Therefore, the present invention can easily incorporate the means to use a single battery, such as one AAA 1.5 V battery to operate this light. One AAA battery will power one high brightness LED for 6-8 hours when the inverter circuit presented in this invention is used. The use of a single 1.5 V battery in this embodiment can therefore be considered as use as a backup to the super capacitor for a power source, or it can be considered to be a primary power source in this embodiment. In other words, the inverter circuit presented in this embodiment provides the means to power a high brightness 4 V LED from a single 1.5 V battery.
The present invention is also proposed for use in five additional lighting applications: In use as an outdoor landscaping light, an outdoor home light, as a bicycle light (front or rear), as a portable reading light, and as a portable indoor house light.
In summary, the present invention solves several problems of the prior art devices, including: (1) battery replacement and disposal problems (for both rechargeable and non-rechargeable batteries); (2) charging speed problems, and the lack of charging options; (3) the limitation of high power use and the replacement problem of incandescent bulbs; (4) the limitation of colored and/or blinking LEDs; (5) energy conservation due to the lack of options in selectively providing a very bright light or less bright light to conserve stored power; (6) and the problem of brightness decay when power from a super capacitor is used to run a LED.
The present invention generally comprises a housing suitable to its particular application, a charging system (a solar panel, a home charger unit, a car charger unit, a crank-generator, or any combination of these), a storage system that will last, in most instances, longer than a typical human lifetime, an electronic assembly for delivering current from the storage system to an LED, and an LED that will never need replacement in ordinary use. The solar panel is positioned on the housing exterior. In addition, the present invention provides the means for quick charging from home or auto power sources, or via a crank-generator system. Also included are more than one white LED that may be selectively used individually or collectively depending upon the need for light output or the desire to conserve power. In another embodiment, the present invention uses one white LED with the option of switching inline a series resistor to cut the power to the LED to xc2xd or xc2xc to double or quadruple the duration of light available. The present invention describes a truly portable light that will never need to be charged by an external electrical source (although it can be quickly charged from external power sources), will never need a battery replacement, and will never need a LED (or a light bulb) replacement in most cases.